721988 has 6 divisors (see below), whose sum is σ = 1263486. Its totient is φ = 360992.

The previous prime is 721979. The next prime is 721991. The reversal of 721988 is 889127.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 521284 + 200704 = 722^2 + 448^2 .

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721988.

It is an unprimeable number.

721988 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 90245 + ... + 90252.

It is an arithmetic number, because the mean of its divisors is an integer number (210581).

2⁷²¹⁹⁸⁸ is an apocalyptic number.

It is an amenable number.

721988 is a deficient number, since it is larger than the sum of its proper divisors (541498).

721988 is a wasteful number, since it uses less digits than its factorization.

721988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 180501 (or 180499 counting only the distinct ones).

The product of its digits is 8064, while the sum is 35.

The square root of 721988 is about 849.6987701533. The cubic root of 721988 is about 89.7105101680.

The spelling of 721988 in words is "seven hundred twenty-one thousand, nine hundred eighty-eight".